Need to figure out how to use the BS2 and the MAX7219 chip with a diplay board
kingspud
Posts: 128
Hello all,
·
I am requesting help from all you EE's, Electrical Gurus, and all around tech heads!
·
I created a project that uses the BS2, a MAX7219 chip, and [noparse][[/noparse]4] 7-segment LEDs displays that show the score for two players on a horseshoe game.· The program works great, "thanks again for help on that project also!” with 4 regular·7-segment displays but I need to get the project to work with displays that need 12vDC.· These are bigger and brighter and can be seen outside!
·
Obviously the MAX7219 chip will not power the 12V display and I know that I need Transistors for each segment and digit lead to get the whole thing working.·
·
A little info up front:
· The way the MAX7219 chip works is all four 7-segment leads for each display are parallel together and a HI voltage is sent to each segment when it needs to light it up.
Now the way each digit is displayed is that a clocking signal is times for each digit and a 0 Volt or LOW·is sent to the cathode of that digit when it wants it to light up.· Or else a HI voltage is sent when it wants the display digit not to light up!· Kind of the reverse thinking when you think about it!
·
Well, my question is... can anyone out there help me design on of the segment leads and one of the digits leads using a transistor?· After that I can wire the rest of the leads. ·I know that I need an NPN transistor for the segment display lead and a PNP transistor for the digit lead.· The problem is I don't know what type or model Transistor to use and the exact circuit design for the connection.
I already fried on MAX7219 chip by using the wrong transistor.· I am not an EE and I don't know all the theory about transistors to understand the current drain on the Transistor or the saturation of the Transistor.
·
If anyone has already done this or knows how to set it up I would be very grateful!· Once this is done I can complete the project!·
·
I am using a separate 12V power supply to power the display circuit and it is wired just how a regular 7-segment display would be... i.e., seven segments + a decimal point and a common cathode!
·
The 12v display max is 500ma all lights displayed and it is a 4 digit display!
·
Any questions please reply and I will answer as best I can!
·
Thanks again,
·
Joe
·
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“Intellectual growth should commence at birth and cease only at death”
Albert Einstein
·
I am requesting help from all you EE's, Electrical Gurus, and all around tech heads!
·
I created a project that uses the BS2, a MAX7219 chip, and [noparse][[/noparse]4] 7-segment LEDs displays that show the score for two players on a horseshoe game.· The program works great, "thanks again for help on that project also!” with 4 regular·7-segment displays but I need to get the project to work with displays that need 12vDC.· These are bigger and brighter and can be seen outside!
·
Obviously the MAX7219 chip will not power the 12V display and I know that I need Transistors for each segment and digit lead to get the whole thing working.·
·
A little info up front:
· The way the MAX7219 chip works is all four 7-segment leads for each display are parallel together and a HI voltage is sent to each segment when it needs to light it up.
Now the way each digit is displayed is that a clocking signal is times for each digit and a 0 Volt or LOW·is sent to the cathode of that digit when it wants it to light up.· Or else a HI voltage is sent when it wants the display digit not to light up!· Kind of the reverse thinking when you think about it!
·
Well, my question is... can anyone out there help me design on of the segment leads and one of the digits leads using a transistor?· After that I can wire the rest of the leads. ·I know that I need an NPN transistor for the segment display lead and a PNP transistor for the digit lead.· The problem is I don't know what type or model Transistor to use and the exact circuit design for the connection.
I already fried on MAX7219 chip by using the wrong transistor.· I am not an EE and I don't know all the theory about transistors to understand the current drain on the Transistor or the saturation of the Transistor.
·
If anyone has already done this or knows how to set it up I would be very grateful!· Once this is done I can complete the project!·
·
I am using a separate 12V power supply to power the display circuit and it is wired just how a regular 7-segment display would be... i.e., seven segments + a decimal point and a common cathode!
·
The 12v display max is 500ma all lights displayed and it is a 4 digit display!
·
Any questions please reply and I will answer as best I can!
·
Thanks again,
·
Joe
·
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
“Intellectual growth should commence at birth and cease only at death”
Albert Einstein
Comments
There is an AppNote on the Maxim website for this. It should be linked from the MAX7219 page. Take care.
Found it...
http://www.maxim-ic.com/appnotes.cfm/appnote_number/1196
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Chris Savage
Parallax Tech Support
If I have any further questions I will let you know!
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“Intellectual growth should commence at birth and cease only at death”
Albert Einstein
I read through the document:
Using the MAX7219/7221 to Drive Higher Voltage or Current
and I know I need to use figure 2:
The circuit of Figure 2 includes a level shifter to allow a higher supply voltage than 5V to be used to drive the LEDs. Q3 operates as a common-base current switch, and sinks a collector current set by resistor R2 (about 5mA using Vcascode = 5V) when the digit drive output is low. This current in turn develops about 5V across the 1kΩ of R3 to provide a consistent gate drive to logic level PFET Q2, independent of the fluctuations of the supply Vdriver. Note, though, that the collector of Q3 can go no lower than VCE(sat)Q3 above it's emitter, which is at VBE below Vcascode.
Figure 2. Current boosting the digit drive using an LED supply 10V or higher.
The display needs 12V to drive the segment sections and is a anode/cathode setup.· Anode for the segments and cothode for the digits.
The problem is I am not an EE and I can't figure out this setup.·
·What is Vcascode and where does it supplied from?
·What are the values of Q2, and Q3?· Vdriver is going to be from a 12V power supply with a max output of 500 mAmp.
I know Q3 is an NPN transistor but what type or model should I use?· If you can help me figure out the circuit layout for just one segment and one digit I would be
incredibly greatful!!!!!
I keep trashing segment leads on my MAX chip!· bummer!
Please help!!!!
Joe
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“Intellectual growth should commence at birth and cease only at death”
Albert Einstein